question_answer

The complex \[{{[Fe{{({{H}_{2}}O)}_{5}}NO]}^{2+}}\] is formed in the brown ring test for nitrates when freshly prepared \[\text{FeS}{{\text{O}}_{\text{4}}}\]solution is added to aqueous solution of \[\text{NO}_{3}^{-}\]followed by addition of conc. \[{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\text{.}\]Select the correct statement about this complex.

A)  Colour change is due to charge transfer

B)  It has iron in+1 oxidation state and nitrosyl as \[\text{N}{{\text{O}}^{+}}.\]

C)  It has magnetic moment of 3.87 BM confirming three unpaired electrons in Fe     

D)  All the above are correct statements

Correct Answer: D

Solution :

  \[\left. \begin{align}   & NO\xrightarrow{{}}N{{O}^{+}}+{{e}^{-}} \\  & F{{e}^{2+}}+{{e}^{-}}\xrightarrow{{}}F{{e}^{+}} \\ \end{align} \right]\]Charge transfer \[\therefore \] Number of unpaired electron, \[n=3\] \[n=3\]Magnetic moment\[\mu =\sqrt{n(n+2)}\] \[=\sqrt{3(3+2)}\] \[=3.87\,BM\] Thus, all the given options are correct.